Udisha
Reflective window film
Heat-reflective tinted window films are extremely affordable and a suitable alternative to expensive blinds. It can be directly attached to the glass window, preventing the harsh sunlight from coming in. This helps cool the room without blocking the window view.
Aluminum foil shield
If you are in need of a quick fix, cover a cardboard with aluminium foil and attach it to the window. Make sure, the aluminium faces the sun so that the light can bounce back. This prevents the room from heating up during summers.
Bubble wrap insulation
Get some bubble wrap and place it on your window by sprinkling some water on the glass surface. The air-pockets significantly slows down the heat from entering while the air pockets act as thermal barrier.
DIY cardboard panels
Cut cardboard to fit your window frame and cover them properly using white paper, newspaper or some light fabric. This can help block the heat when the sun is harsh, providing a quick hack that you can make yourself in minutes.